Ferric Chloride

LoopyByteloose

I am sitting here with a first tray at copper clad circuit board sitting in 500ml of Ferric Chloride.

This is a first attempt and it just seems to not be doing much.· All this may sound silly, but I do need some practical advice as the web sites just tell· you to buy their product, etc.

I really cannot import chemicals like this.· The local documents are in Chinese, so I am trying to find a standard hobby porceedure.

Firstly, I put 25 grams in 500ml of water.· It seems to be far too weak.· I simply bought the smallest packet at the store and guessed this would be about right.· The girl behind the counter said that the Developer for the light sensitive board was mixed one packet/per 500ml.· I just figured the FeCl3 to be the same deal.

Secondly, I have not heated it because getting corrosive chemicals up to 70 degrees centigrade in my small room just seemed a bad way to begin.

Thirdly, I really cannot find any information on how to properly dispose of the used chemical.· While Taiwan does have quite a cocktail of things going down its drain, I would rather be part of·the solution rather than part of the problem.

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Having said all that, it seems obvious that I should make the solution stronger.
I really need input from someone who has been there and done that.

It seems that the 'old school' believes in getting the Ferric Chloride as warm and as strong as possible.· They also give lots of warnings about stains, chemical burns, and fumes.

Alternatively, I looked up some material from people that do etchings as fine art work [noparse][[/noparse]they use the Ferric Chloride with copper plate itaglio].· One site came out with an very interesting enhancement [noparse][[/noparse]the Edinburg Mordant].· It seems the additon of Citric Acid to the Ferric Chloride solution will enhance its efficency.· It has something to do with freeing up ions that are tied to water molecules.

Also, the Citric Acid comes in powdered for as a food preservative and baking supply.· It seems a lot more appealing that boiling hot corrosives.

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Any suggestions and comments are welcome.



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G. Herzog in Taiwan

Newzed

The ferric chloride needs to be quite strong and should be heated to at least 100 degrees.· Put your copper and the ferric chloride in a heavy duty plastic bag inside another heavy duty plastic bag. This will allow you to agitate the solution, which is essential to good etching.· The ferric chloride can be neutralized by adding very small amounts baking soda.· This should be done is a glass tray, outside, since the reaction will generate a little heat.· Continue adding baking soda until there is no evidence of a reaction.· The resulting products, ferric carbonate, salt and a tiny bit of hydrogen gas, can be flushed down the drain.

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Sid Weaver
Do you have a Stamp Tester yet?
http://hometown.aol.com/newzed/index.html

·

Forrest

Ferric Chloride will work at room temperature - but etching will be slower. For 1 ource copper - it may require 20-40 minutes to etch the copper. It's a good idea to slowly agitate the solution every 2-5 minutes. As Newzed said, baking soda will neutralize the solutions and I also use it to neutralize the board (after removing your pattern).

LoopyByteloose

Thanks, I got my board out after adding another 50 grams after waiting 2 hours. It took 3 hours total to etch. Obviously too weak a starting solution.

Still, I think I prefer working at room temperatue. The fumes are something that put me off.

This was somewhat of a trial run. One of the two projects came out bad due to the art work being to detailed and not clear enough on the exposure.

Nonetheless, I am quite satified. I know where I need to improve. I will just have to figure out where I can buy some baking soda and how to ask for it in Chinese.

I am finding that drilling the holes by hand with a pin vise and looking through binocular magnifiers is best. I can center the drill bit by eye and without using power I can control its movement and location quite well. So, this is certainly going to be a handcrafted board.

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G. Herzog in Taiwan

Manuel

Hello:
I use a premade solution, which does not hurt if i touch, and it takes me 10 minutes for my board to be ready

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Best Regards

Manuel C. Reinhard

Orion

Most home kits for etching use a fish tank air pump to continually agitate the enchant. This is a cheap way to speed it up.

Forrest

Next time you mix up the Ferric Chloride solution, use medium hot water (120F) and use half as much water as you did the first time. There shouldn't be any fumes at that temperature - and the solution will slowly cool to room temperature. FYI I normally buy my Ferric Chloride in liquid form - costs $4.29 for 16 oz. at Radio Shack.

Beau Schwabe

Ahhhh..... Liquid Rust

Nasty Nasty stuff!! --- Ahem!! (still have that cough)

As others have said baking soda works well to neutralize the stuff, but you can also use
soda-ash found where swimming pool chemicals are sold.

When I did a lot of this, I designed a "rocking" agitator that was heated on the bottom.
This worked really well in a short amount of time. A slow rotating motor about 15 rpm
with an offset moment arm connected to the base plate (teeter-totter).... Now days I
would probably use a servo and a Stamp..... with a timer, alarm, temp monitor, etc..

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

steve_b

In College, one of the students built an etching chamber!
BAsically a fishtank pump pushed the solution through some PVC with some small spray nozzles that would spray on to the board (held vertically).
There was an inline heater to keep the solution at a nice "working" temperature.
This would take less than 20minutes and would allow you to make more than one board at a time and reuse the solution (add a bit more for strenth I think).

You also didn't need to sit and babysit it or agitate it every X minutes!!

Waiting 2-3hours seems WAY long! Just agitate it and it should only take 15-20minutes.

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·

Steve

"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."

mediaprefect

Kramer,

I have always kept my used ferric chloride solution for re-use. It's hard to make it too strong and if you save it for use again, the disposal problem is seldom encountered by the casual user. I use a Pyrex baking dish with a layer of marbles on the bottom and lay the single sided board on them copper side up for etching. When I used to etch boards more often, I built a mechanism to rock the glass tray for quicker etching. The layer of marbles is inert and acts as a bearing base to allow the board to slide imersed in the etchant keeping fresh etchant in contact with the copper. To heat the etchant I use a heat-lamp suspended over the tray. Water can always be added to make up for evaporation. I have sometimes let it get quite hot while prepping the bare boards with no problem. If you etch too long though, you can get undercutting of traces. Low tech and small investment.

Note: If you use ammonium persulphate as an etchant, do not use much heat as it will decompose if you get it to hot. Also the mixed solution does not have a long shelf life for use again. Ferric Chloride is stable and a solution can be kept ready for use for years with no change.

Finally, I am curious as to what the other members are using to make boards. I still use Kodak photoresist (KPR) to coat cleaned boards, dry, expose, solvent wash, dye, inspect and etch. If I get a bad exposure, I just scrub the board and coat it again. Do any others in this group use this old method or does everybody use pre-sensitized boards or the toner/transfer methods?

Rick

Beau Schwabe

I have tried several toner transfer methods with some success (Press-N-Peel) ,
but I tend to lead toward the photoresist as a preference.

Once you get your exposure time right it's much easier.

Exposure pre test:
Take a scrap piece of the photoboard, cover with a piece of black construction paper.
Under FIXED lighting conditions pull the construction paper partially out on 5 minute
intervals gradually exposing more and more of the board. Go ahead and etch this
piece in the FeCl , you will see a definate "sweet spot" for the proper time interval
that you should use.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Kenny Gardner

With the Pulsar Toner Transfer system, it literally only takes a few minutes to etch a board. No agitation. Just a sponge and a small amount of Ferric Chloride.

I was very skeptical, but it actually does work.

http://www.pulsar.gs/PCB/a_Pages/1_Menu/Overview.html

Kenny


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--

Kenny Gardner
GAP Development Company
http://www.gapdev.com/
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Bean

I also use the Pulsar system, and it works great. I don't use the sponge because it's kinda messy. I just let it soak, I'm usually not in that big a hurry.
It's cheap too. Only $100 and that includes the laminator (0.032" thick boards only though).
Bean.

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"SX-Video·Module" Now available from Parallax for only $28.95

http://www.parallax.com/detail.asp?product_id=30012

Product web site: www.sxvm.com

"One experiment is worth a thousand theories"
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LoopyByteloose

Toner transfer is out.
From what I read and what I tried, it just seemed to require to many fixes.
Also, some of the glossy paper jambs the laser printers, other may make the machine dirty and require running 5-10 copies to clean it up.

The photoresist is available here and if I can just get a sheet of clear glass to hold down my art work, I will be set.
My first attempt was a bit blurred in places, but developed quite easily.

I can print transparencies on my Hp deskjet 3420 [noparse][[/noparse]though they do smear if handled roughly] or I can print transparencies on other people's printers and/or copiers.

Regarding Pulsar's system. It isn't sold here and it is really difficult to import these kind of chemicals. The web sites usually say NOT FOR EXPORT. Still, it sounds great.

Congradulations on the 'SX-Video Module'. It am quite interested but I have to confess that a refuse to own a TV. It interfers with my reading real information.

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G. Herzog in Taiwan

Orion

Photoresist, man myself. Inkjet on transparencies, etch with chloride with pre-sensitized boards. Great tip on the exposure Beau! Anyway I have got down to .02" traces and .01" should be doable. I ground plane everything to save on the enchant. It saves enchant but costs ink!


Now if I had a milling machine for the holes.... life would be grand! The hate of drilling hole is driving me to smd work. I would rather send the time to solder than drill.

bobledoux

I'm using the Pulsar system and it works every time. No chemicals are required except for the Ferric Chloride. The sponge etching technique eliminates any special hardware for etching. No heating of chemical is required. It also allows you to prevent undercutting on thin traces. My SMD boards utilize .012 traces and they come out fine.

Good quality toner seems important to good results. I print the design on a blank piece of paper. The printed area is cut out. A small piece of toner transfer paper is taped over the cutout area, using a laser label as tape. This assembly is reprinted. This process results in very economical use of the expensive toner transfer paper.

Post Edited (bobledoux) : 8/23/2005 1:23:32 PM GMT

David B

Why such despair over drilling holes?

I used to use a trick that made hole drilling really easy. I'd design my circuit on paper, then sketch out a parts layout. I'd insert the parts into one of those 4 by 6 perfboards that are predrilled in 0.1 inch spacing. I'd use a sharpie to mark where the leads stuck through, then remove the parts. I'd lay the perfboard onto a blank copper-clad board, then use a hand dremel to drill where I'd marked. Using the predrilled board as a drilling guide helped immensely - there was practically no positioning needed; I could drill dozens of holes a minute. (For the next circuit, I'd just sand the sharpie markings off the predrilled perfboard and start again.)

Then I'd use a sharpie to draw the circuit onto the copper, using the holes as a guide, and etch the board with a Radio Shack etching kit.

I've made dozens of boards this way. They are kind of ugly, though, and the hand-drawing gets difficult on larger circuits. If only I had a cheap milling machine that could mill nice-looking boards...